The present invention relates to a process and an apparatus for determining, without contact, a three-dimensional surface profile of the interior of a furnace, particularly of the surface of the charge in a shaft furnace or of the burden in a blast furnace.
With the recent development of the bell-less charging apparatus, as disclosed for instance in the U.S. Pat. No. 3,693,812 to R. Mahr et al., it has become possible to introduce a charge into a furnace and distribute it in any desired manner therein. This apparatus also makes it possible to compensate for local subsidence of the charge or burden by replenishing the charging material at points where this has occurred, thus restoring the desired surface configuration of the charge or burden. Therefore, charging apparatus is available to restore the surface of the burden to an optimum configuration throughout the entire furnace if the surface profile can be accurately determined. Thus, it is extremely desirable to be able to determine the exact and complete surface profile of the charge or burden, either continuously, or at least at regular intervals.
Mechanical profilometers are a known means for determining surface profiles, but the operation of these devices requires that a probe be introduced either vertically or horizontally into the furnace, and then into direct contact with the surface of the burden. An example of such a profilometer is disclosed in U.S. Pat. No. 3,816,932. Such mechanical profile probes suffer a serious drawback in that the primary measuring elements are exposed to rigorous conditions, as regards temperature, dust, and corrosion, caused by the blast furnace top gas. Thus, they undergo rapid wear and require expensive regular maintenance. A second serious drawback of the mechanical probes is that during the lengthy period in which the measuring elements are in the furnace the charging process must be delayed.
Attempts have also been made to determine the surface profile of the furnace charge by punctiform (point-by-point) scanning with electro-magnetic, ultrasonic and radio-active rays. By comparison with the mechanical devices, these profilometers offer the advantage that they operate by a contactless system, i.e. without any mechanical contact with the surface to be measured. However, the known radiation profilometers operate with a focused beam, and only one point at a time can be measured on the surface of the charge. Thus, with these devices the surface must be scanned point by point, in which process the radiation profilometer must perform a mechanical movement in separate steps. Such methods usually enable the profile to be determined in only one plane of intersection with the surface of the charge; a profile picture extending over a number of such planes would necessitate a corresponding number of different radiation profilometers of the same type, positioned at different points in the head of the blast furnace.